Electrolytic bipolar alkali chlorate cell



Jan. 17, 1967 s. FORBES 3,293,946

v Q ELECTROLYTIC BIPOLAR ALKALI CHLORATE CELL Original Filed MarchBO.1962 3 Sheets-Sheet l INVENTOR. SYDNE'Y FORBES A TTOKNE Y ELECTROLYTICBIPOLAR ALKALI CHLORATE CELL Original Filed March so, 1962 sSheets-Sheet 2 'INVENTOR. .s'mlve'y r0255 A TfOR/VEY Jan. 17, 1967 s.FORBES 3,298,946

ELECTROLYTIC BIPOLAR ALKALI GHLORA'TE CELL Original Filed March 30, 19623 Sheets-Sheet 3 mdr United States Patent 3,298,946 ELECTROLYTIC BIPOLARALKALI CHLORATE CELL Sydney Forbes, Pittsburgh, Pa., assignor toPittsburgh Plate Glass Company, Pittsburgh, Pa., a corporation ofPennsylvania Original application Mar. 30, 1962, Ser. No. 183,974, nowPatent No. 3,203,882, dated Aug. 31, 1965. Divided and this applicationNov. 3, 1964, Ser. No. 408,615 3 Claims. (Cl. 204-268) This is adivision of U.S. Serial No. 183,974, now US. Patent 3,203,882, filedMarch 30, 1962.

The present invention relates to chlorate cells. More particularly, thepresent invention relates to a novel electrolytic bipolar chlorate cellsuitable for use in the manufacture of alkali metal chlorate from alkalimetal chloride solutions. Still more particularly, the present inventionrelates to a novel apparatus for safely conducting the electrolysis ofalkali metal chlorides to produce alkali metal chlorates.

For a complete understanding of the present invention, reference is madeto the accompanying drawing in which:

FIGURE 1 is a plan view of the top of the novel chlorate cell of thepresent invention shown the positioning of the current distributors,hydrogen outlets and brine feed inlets.

FIGURE 2 is a side elevation partly in section of the cell shown inFIGURE 3 and taken along lines 11-11 of FIGURE 3.

FIGURE 3 is a plan view partly in section of the cell shown in FIGURE 4with the cover removed to show the electrodes and with the electrodespartly removed to show the bottom construction of the cell.

FIGURE 4 is an end view of the cell partly in section showing the busbarconnection to the cell and the liquid produced discharge eduction pipes.

Turning in particular to FIGURES 1, 2, and 3, there is shown a covermember 1. The cover member of the cell is bolted to the side 3 by aplurality of bolts 2 which traverse a flange member 11 aflixed to orformed as an integral part of the side member 3. Between the covermember 1 and the flange member 11 is a rubber lining 12 and an asbestosgasket 13 to prevent leakage from the side of the cell. Located slightlyabove the upper surface of the cover member 1 of the cell is a brineheader 14. A plurality of feed pipes 15 are integrally connected to theheader 14 and these feed pipes terminate in downward extensions whichtraverse the cell cover and end as an open tube a short distance belowthe liquid level contained in the cell. Preferably, these feed pipes 15terminate'at a level below the surface of the brine contained in'thecell of about 6 to inches. The header 14 is fed from a duct 16 whichnormally is connected to a retention tank (not shown), and which islocated at a point some distance from the cell.

The admission of brine to the cell is readily accomplished by suitableconventional pumping mechanisms not shown in the cell drawing. Theadmission of brine to the cell at the various points therein may bereadily regulated by regulating the orifice size of the opening at thedownward extension of the feed pipe 15. Thus, where desired, feed ratesto any one unit within the cell box may be regulated by providing alarger or smaller orifice on this feed pipe to thereby regulate fluidflow into this portion of the cell.

Located preferably on the opposite end of the cell from the inletopenings 18 for the brine feed are a plurality of hydrogen outlets 19which are in communication with a gas collection zone 20 having areduced cross sectional area in relation to the cross sectional area inthe cell in which it is located. This gas collection zone 20 has amechanism well understood in the art.

cover member 21 located thereon and this is preferably constructed of apolyvinyl chloride or other similar acid cubic area present in zone 20and the easily rupturable window thereby considerably minimize theeffects of any hazardous accumulation of oxygen in the hydrogen outletsof the cell.

Drawing attention particularly to FIGURE 2, a plurality of anodeconnectors or current distribution rods for the electrodes of the cell31 are shown. These rod members 31 are held in place by a collar member32, preferably constructed of graphite which in turn is held in placewith relationship to the cover of the cell by a clamping member 33. Arubber lining 34 is located beneath the cover surface 1. The entireinterior surface of the cell, that is, the sides and the bottom, islined with various materials to prevent corrosive attack at these brineexposed surfaces. Thus, the side of the cell 39 is lined by a rubberlining 35 which in turn has aflixed to the inside surface thereof brickmembers 36. These bricks are preferably constructed of acid resistantceramic materials. Similarly, the bottom of the cell has a rubber lining37 aflixed thereto and this rubber lining has several layers of brickoverlying it. The rubber lining protects the steel surface of the bottomof the cell 38 from corrosive attack during electrolysis. Similarly, therubber lining 35protects the side members 39 from corrosive attackduring electrolysis. The bricks are placed against the rubber lining toprevent serious corrosive attack of the rubber lining duringelectrolysis by providing a rather tight interface between the rubberand the surface of the brick. In actual operation when fluid leaksthrough the brick and begins attacking the rubber surface the tightphysical connection between the brick and the rubber lining prevents anaccumulative deterioration of the rubber lining and ultimately protectsthe steel from corrosion.

As shown in FIGURE 4, busbars 40, used to supply current to the cell ofthe instant invention, are connected through electrical connectors 41 tothe anodes of the cell through the current anode distribution rods 31 byan electrical clamping member 42. The busbars 40, electrical connectors41 and clamping member 42 are preferably constructed of copper and theconnectors 41 are bolted to the clamping members 42 with copper bolts43.

'- J Further, as shown in FIGURE 4 in the bottom portion the spacingmembers 44. Located in the bottom of each cell unit is an educator pipe45 which removes the liquid products of electrolysis to a common header46 located in the bottom of the cell. The header 46 has a dischargeconduit 47 connected thereto on the outside portion of the cell andmaterial removed from the cell through this conduit is fed to aretention tank where it is held for a period of time sufficient toconvert the hypochlorous acid contained therein to alkali metalchlorates by a chemical A portion of the material contained in theretention tanks as has previously been explained is returned to the cellalong with makeup alkali metal chloride solution for furtherelectrolysis. This portion of the operation of the chlorate cell is notshown in the drawings since it has no relationship to the novel methodof operating these cells or to their construction.

Turning to FIGURE 2, it is to be noted that the cell is so constructedthat the top member 1 slopes from the gas collection zone 20 to thebrine inlet opening 18. The particular pitch of the slope is not ofparticular consequence, though preferably an incline providing a drop ina vertical direction of about inch per running foot or more ispreferred. The sloping top permits the collection of gas bubbles on theundersurface of the cover member 1 at the rubber lining 12 and assistsin transporting these gas bubbles as they collect at this surface to thegas collection zone of reduced cross sectional area 20.

The electrode current distribution rods 31 and their connection to theend blocks 50 of the cell are shown more distinctly in FIGURE 3. In thisfigure there is shown the current distribution rod 31 positioned withina graphite collar 32. The graphite collar 32 is externally threaded andadapted to be received into an internally threaded graphite end block.The internal threading in the graphite end block is located on the upperend of two bored holes located in the end block and traversing the endblock along its long axis. The bored holes terminate slightly above thelower surface of the end blocks. The current distribution rods 31 arepositioned inside of the collar and are held in place therein and in theend block by tamping amalgam between the outer surface of the rods 31and the inner surface of the collar 32 and the bored holes. The lateralsurface 52 of the end block 50- is machined on its long axis to providefour elongated channels 53. These channels are constructed and adaptedto receive one end of the electrodes 54 utilized in the cell and aresufficiently long to provide for the insertion of at least seven anodeblades of conventional dimension one above the other.

As shown in FIGURE 3, the electrical current is passed through the cellby introducing current through rods 31 to the end blocks 50. The currentpasses from the end block 50 into the inserted end of the electrodes 54.The electrodes 54 operate in a bipolar fashion so that current passesfrom one end of the electrode to the other and from here is distributedacross the electrolyte to the next adjacent electrode which then becomesan anode and carries current to the next adjacent electrode. Theelectrodes are separated one from the other by virtue of nonconducting Hspacers 55 located between them. Thus, in operation of the cell currentwill travel from electrode to electrode as depicted bythe small arrowsshown in FIG- URE 3. Current distribution rods such as those shown inthe drawing are also located on the other end of the cell which is notshown in FIGURE 3. These distribution rods are located in end blocks inexactly the same fashion as those shown in the drawing and at this pointcurrent is removed from the cell by passing through the electrodes intothe end block and from the end block into the distribution rods and fromthere to the bus system.

In the operation of a cell of this character, because of the physicalrelationship of the current distribution end blocks to the first cellunit contained in the cell and the last cell unit contained in the cell,considerably more heat is evolved in the first and last physical unitsformed by the spacing members 44 within the cell. Since this heat of theelectrolyte considerably influences the rate of electrolysis in a givencell unit, brine feed rates to the first and last units of the cell areusually slightly higher than those to the intermediate cells locatedbetween the first and last cells. This may be readily accomplished, aspreviously explained, by regulating the brine orifices feeding the firstand last cell units. Usually, this feed rate is such that brine fed tothe first and last unit in the cell is at least 20 percent greater thanthe rate of that utilized in feeding intermediate cells. This is animportant consideration in the operation of a cell of this charactersince if possible, even anode wear from one end of the cell to the otheris the most desirable condition for proper and economical electrolysis,Unifonm temperatures throughout the cell help achieve this uniform wear.If desired, current may be reversed in the cell from one end to theother periodically to provide for more even wear of the electrodesduring electrolysis. Even wear of the electrodes during electrolysisprovides a uniform electrode gap across the electrolyte contained withinthe cell and considerably reduces any large voltage fluctuations whichnormally result when large electrode gaps are encountered in this typeof cell.

The electrode materials employed in a cell of this type are normallygraphite and graphite electrodes form the preferred embodiment of theinstant cell. While graphite is preferably employed, it is of course tobe understood that other electrode materials capable of withstanding thecorrosive conditions existing within the electrolyte may also beemployed if desired. Thus, certain base metals such as titanium andtantalum may be utilized as electrodes when they are provided with asuitable platinum surface on which the electrolysis may take place. Inaddition, various combinations of electrode materials may be employedwhere desired. Thus, if desired, platinum plated or coated titanium. ortantalum may be employed as anodes and these anodes provided at one endwith an integral steel cathode so that the entire structure along theelectrical path of the cell operates as an anode at one end and acathode at the other. The end blocks 50' of the cell are preferablyconstructed of graphite, usually a corrosion resistant dense graphitematerial such as karbate. While this is preferred, it is of course to beunderstood that machined steel may also be employed or any otherelectrically conductive metal which can be readily bored and machined toprovide the necessary holes and channels for the electrical connectingrods 31 and the electrodes 54. In this latter case, care must be takento provide for suitable corrosion resistant lining on those surfaces ofthe end block which are exposed to brine when placed in the cell.

In the operation of a cell such as shown in FIGURES 1-4 the cell isfilled to a point such that the electrodes are covered with brine andthe brine level in the cell is at least partially contained in therestricted gas collection zone 20. Electric current is passed throughthe cell via the connectors 31, end blocks 50, electrodes 54 and out theother side of the cell. During electrolysis, brine is fed to the cellthrough header 14 and feed pipes 15 to all of the cell units formed bythe spacers 44. The first and last units in the cell, that is, the unitsadjacent to the electrical distribution system have the orifices intheir feed pipes 15 adjusted to provide a brine flow 20 percent greaterthan the other units in the cell. During electrolysis, hydrogen releasedin the cell is caused to collect under the cover of the cell in thebrine. The collected gas bubbles are then transported across the coverby virtue of its upward slope to the restricted gas collection zonewhere it is removed from the cell. Operating the cell in this manner,uniform temperatures are readily provided during electrolysis. Inaddition, the gaseous hydrogen is rapidly collected and removed from thecell.

While this invention has been described with reference to certainspecific embodiments, it is of course to be under- .stood that theinvention is not to be so limited except insofar as appears in theaccompanying claims.

What is claimed is:

1. An electrolytic alkali metal chlorate cell comprising an enclosedbox, a plurality of bipolar electrodes in said box constructed andarranged to electrolyze brine in said box, means to pass current throughsaid box and across said electrodes, an inclined cover member on saidbox,

a gas collection zone located beneath said cover at the upper end of theinclined surface, said gas collection zone being restricted in size andprovided at the cover surface with a rupturable disc, and means to passelectrolyte into said cell and remove the liquid products ofelectrolysis therefrom.

2. Apparatus of claim 1 wherein said disc is constructed of polyvinylchloride.

3. An electrolytic alkali metal chlorate cell comprising an enclosed boxhaving a plurality of elongated end blocks located at one end thereinand extending from the top of the cell to a point slightly above thebottom, said end 'blocks being provided on their upper surface With twobored holes which traverse the end blocks to a point slightly above thebase thereof, conductor rods in said holes, a plurality of channelslocated on the lateral surface of said end blocks and having a pluralityof electrodes inserted therein, a plurality of end blocks of similarconstruction located on the opposite end of said box, means forintroducing electrical current into said box and removing currenttherefrom at the opposite end of said box, a cover member on said boxhaving a sloping surface, said sloped sur- References Cited by theExaminer UNITED STATES PATENTS 1,092,369 4/1914 Kolsky 20495 1,837,51912/ 1931 Bleecker 204268 1,994,125 3/ 1935 Eck 204-278 2,468,022 4/ 1949Blue et a1. M 204-244 2,799,643 7/ 1957 Raetzsch M 204270 JOHN H. MACK,Primary Examiner.

E ZAGARELLA, Assistant Examiner.

1. AN ELECTROLYTIC ALKALI METAL CHLORATE CELL COMPRISING AN ENCLOSEDBOX, A PLURALITY OF BIPOLAR ELECTRODES IN SAID BOX CONSTRUCTED ANDARRANGED TO ELECTROLYZE BRINE IN SAID BOX, MEANS TO PASS CURRENT THROUGHSAID BOX AND ACROSS SAID ELECTRODES, AN INCLINED COVER MEMBER ON SAIDBOX, A GAS COLLECTION ZONE LOCATED BENEATH SAID COVER AT THE